diff --git a/pyrightconfig.json b/pyrightconfig.json
index f032c9c..3b66687 100644
--- a/pyrightconfig.json
+++ b/pyrightconfig.json
@@ -6,5 +6,6 @@
   "ignore": [
     "**/.vscode/**",
     "**.ipynb"
-  ]
+  ],
+  "reportInvalidTypeForm": false
 }
diff --git a/stormvogel/mapping.py b/stormvogel/mapping.py
index bdfffd1..b3e30c0 100644
--- a/stormvogel/mapping.py
+++ b/stormvogel/mapping.py
@@ -1,11 +1,9 @@
 import stormvogel.model
 
 try:
-    import stormpy.storage
-
-    stormpy_installed = True
+    import stormpy
 except ImportError:
-    stormpy_installed = False
+    stormpy = None
 
 
 def stormvogel_to_stormpy(
@@ -25,6 +23,7 @@ def build_matrix(
         Takes a model and creates a stormpy sparsematrix that represents the same transitions
         """
 
+        assert stormpy is not None
         row_grouping = model.supports_actions()
         builder = stormpy.SparseMatrixBuilder(
             rows=0,
@@ -62,6 +61,7 @@ def add_labels(model: stormvogel.model.Model) -> stormpy.storage.StateLabeling:
         """
         Takes a model creates a state labelling object that determines which states get which labels in the stormpy representation
         """
+        assert stormpy is not None
 
         state_labeling = stormpy.storage.StateLabeling(len(model.states))
 
@@ -82,6 +82,8 @@ def add_rewards(
         """
         Takes a model and creates a dictionary of all the stormpy representations of reward models
         """
+        assert stormpy is not None
+
         reward_models = {}
         for rewardmodel in model.rewards:
             reward_models[rewardmodel.name] = stormpy.SparseRewardModel(
@@ -94,6 +96,7 @@ def map_dtmc(model: stormvogel.model.Model) -> stormpy.storage.SparseDtmc:
         """
         Takes a simple representation of a dtmc as input and outputs a dtmc how it is represented in stormpy
         """
+        assert stormpy is not None
 
         # we first build the SparseMatrix
         matrix = build_matrix(model, None)
@@ -118,6 +121,7 @@ def map_mdp(model: stormvogel.model.Model) -> stormpy.storage.SparseMdp:
         """
         Takes a simple representation of an mdp as input and outputs an mdp how it is represented in stormpy
         """
+        assert stormpy is not None
 
         # we determine the number of choices and the labels
         count = 0
@@ -158,6 +162,7 @@ def map_ctmc(model: stormvogel.model.Model) -> stormpy.storage.SparseCtmc:
         """
         Takes a simple representation of a ctmc as input and outputs a ctmc how it is represented in stormpy
         """
+        assert stormpy is not None
 
         # we first build the SparseMatrix (in stormvogel these are always the rate transitions)
         matrix = build_matrix(model, None)
@@ -186,6 +191,7 @@ def map_pomdp(model: stormvogel.model.Model) -> stormpy.storage.SparsePomdp:
         """
         Takes a simple representation of an pomdp as input and outputs an pomdp how it is represented in stormpy
         """
+        assert stormpy is not None
 
         # we determine the number of choices and the labels
         count = 0
@@ -236,6 +242,7 @@ def map_ma(model: stormvogel.model.Model) -> stormpy.storage.SparseMA:
         """
         Takes a simple representation of an ma as input and outputs an ma how it is represented in stormpy
         """
+        assert stormpy is not None
 
         # we determine the number of choices and the labels
         count = 0
@@ -289,6 +296,8 @@ def map_ma(model: stormvogel.model.Model) -> stormpy.storage.SparseMA:
         return ma
 
     if model.all_states_outgoing_transition():
+        assert stormpy is not None
+
         # we make a mapping between stormvogel and stormpy ids in case they are out of order.
         stormpy_id = {}
         for index, stormvogel_id in enumerate(model.states.keys()):
diff --git a/tests/test_mapping.py b/tests/test_mapping.py
index 2099805..9ac1edf 100644
--- a/tests/test_mapping.py
+++ b/tests/test_mapping.py
@@ -12,12 +12,8 @@
 import examples.simple_ma
 from stormvogel.model import EmptyAction
 
-try:
-    import stormpy
 
-    stormpy_installed = True
-except ImportError:
-    stormpy_installed = False
+import stormpy.storage
 
 
 def sparse_equal(
diff --git a/tests/test_model_checking.py b/tests/test_model_checking.py
index 646439f..34d8d15 100644
--- a/tests/test_model_checking.py
+++ b/tests/test_model_checking.py
@@ -3,12 +3,7 @@
 import examples.die
 
 
-try:
-    import stormpy
-
-    stormpy_installed = True
-except ImportError:
-    stormpy_installed = False
+import stormpy
 
 
 def test_model_checking():
diff --git a/tests/test_result.py b/tests/test_result.py
index 21c5620..cf0a26d 100644
--- a/tests/test_result.py
+++ b/tests/test_result.py
@@ -1,12 +1,8 @@
 import stormvogel.result
 import pytest
 
-try:
-    import stormpy
 
-    stormpy_installed = True
-except ImportError:
-    stormpy_installed = False
+import stormpy
 
 
 def test_convert_model_checker_results_dtmc():